RESPITATION

Releasing energy.

• Cellular respiration is the breakdown of chemical substances, such as glucose, within living cells of both plants and animals for the purpose of releasing energy.

• This energy is used to synthesize the special phosphorus compound adenosine triphosphate, or ATP.

• ATP serves as the energy carrier of the cell and as a convenient form for the temporary storage of chemical energy.

• Nearly all of a cell’s life processes are powered by .ATP.

• The energy to produce ATP may come from any of several sources, including carbohydrates (primarily glucose), fats, and even proteins if the cell is short of food.

• Cellular respiration involves several steps.

1. The first step takes place in the cytoplasm and involves partially breaking down glucose, producing about 2 molecules of ATP for each glucose molecule broken down.

• Anaerobic cells (cells that do not use oxygen) rely totally on this step for all of their energy

• In aerobic cells (cells that use oxygen), additional steps take place in the mitochondria, where food molecules are combined with oxygen in a process known as oxidation.

• The ATP which is produced (about 30 molecules of ATP for each original molecule of glucose) is transported from the mitochondria to all parts of the cell.

• ATP is a readily available source of energy in the cells of all organisms.

• Respiration permits an organism to carry on the functions necessary to maintain life.

• During the process, the organism’s cells releases energy for their own use and produce carbon dioxide and water as waste products.

• The chemistry of respiration is the same in all organisms, because all living things are built on the same general pattern

• The pattern designed by the Creator Himself’.

Opposite processes• Both photosynthesis and respiration convert

energy into a form that living cells can use: • However generally speaking, cellular respiration

is the opposite of photosynthesis.• During photosynthesis, water molecules are first

split into hydrogen and oxygen and then the hydrogen atoms are combined with carbon dioxide to form glucose.

• The opposite occurs during resporation• hydrogen is split from the glucose molecule and

is then united with oxygen to form water. • All that remains of the glucose molecule, after it

is split apart, is the carbon dioxide.

You should be able to• An organism is alive when all its cells are respiring. • understand the function of ATP;• describe the process of aerobic respiration;• distinguish between aerobic and anaerobic

respiration• describe the uses of anaerobic respiration to Man• understand that respiration takes place at the level of

the cell; • understand simple investigations that show the

products of resoiration.

Aerobic respiration

• Respiration is the process by which the energy in food is made available for a cell to do the work necessary to keep it alive.

• When oxygen is used in the reaction, we call it aerobic respiration. The process is catalysed by enzymes and is also called cellular, internal or tissue respiration.

Quiz

• What is the purpose of respiration?

A: During respiration, the energy from the food eaten by an organism is made available.

This energy can he used to carry out all the characturistics of life, movement, growth, reproduction, and so on.

Quiz

• When do animal cells and plant cells respire?

• Animal cells respire all the time because the animal is in constant need of energy. Plant cells also respire all the time. During the day. while sunlight is available, plants also photosynthesise, hut they never stop respiring.

How do the food and oxygen get to respiring cells?

• Food -In animals food eaten is digested and absorbed into the bloodstream.

• The end-products of digestion eventually reach all the body cells.

• In plants the food made in photosynthesis in the leaves travels around in phloem tubes and eventually reaches all cells in the plant.

• Oxygen — In vertebrates, oxygen comes from the air that is inhaled into the lung

• It diffuses into the bloodstream and is transported to all the body cells.

• In plan some of the oxygen comes from photosynthesis and some through diffusion in through the leaves and other parts of the plant.

• In both plants and animals the type of food used for making energy is usually glucose.

• Energy is released when it combines with oxygen (the oxidation of glucose).

• Carbon dioxide is a waste product of this reaction.

• In vertebrates it diffuses back into the bloodstream, to he taken to the lungs and exhaled out of the body.

• In plants it is used for photosynthesis during daylight.

• Respiration or cellular respiration occurs in a series of steps, each of which is catalysed by enzymes.

• The overall process can be summarised in words or by the equation below:

• glucose + oxygen →energy + carbon dioxide + water

• Equation:C6H1206 + 602 → energy + 6C02+ 6H2O

• During aerobic respiration glucose is broken down completely into carbon dioxide aria water.

• At each step in the breakdown of glucose, energy is released.

• This is used to convert a chemical called ADP into adenosine triphosphate (ATP).

• Each molecule of ATP acts as a little ‘packet’ of energy.

• The energy can be stored and used later when needed.

Advantages of storing energy in small packets

• There are many advantages of storing and using energy in small packets like this.

• The energy can he released from ATP wherever and whenever it is required by a cell.

• The energy can he released rapidly.

• Energy is not wasted. A large amount of energy is released by oxidising one glucose molecule and many ATP molecules are formed. A cell may not require very much energy at once. By storing the energy in small packets of ATP molecules, the cell can use small amounts of energy as required.

• The energy can be used to drive many different chemical reactions rapidly.

• Energy can he stored as ATP in one part of a cell and transported and used else where without causing reactions in between.

• Energy production and utilisation are very efficiently and carefully controlled by the cell.

• Respiration occurs in an organelle called the mitochondrion.

• Mitochondria are present in all cells, animal and plant. and are sometimes referred to as the ‘power houses’ of the cell.

• The energy stored in ATP (adenosine triphosphate) is released when it is converted to ADP (adenosine diphosphate)

• The energy stored in ATP

(adenosine triphosphate) is released when it is converted to ADP

(adenosine diphosphate)

Quiz

• What is the important product of respiration? What are the waste products of respiration?

• The important product of respiration is energy, which an organism needs to carry out the characteristics of life. The waste products of respiration are carbon dioxide arid water.

Quiz

• Where does respiration occur?

• Respiration occurs in the mitochondria of cells.

Quiz

• Give three reasons why it is advantageous to store energy in small packets.

• Energy is released only when necessary; only as much energy as is needed is used; energy is released rapidly when it is needed.

Anaerobic respiration

• Respiration can also occur without oxygen and this type of respiration is called anaerobic respiration.

• Both anaerobic and aerobic respiration involve the breakdown of glucose,

• However in anaerobic respiration it is not completely broken down.

• Habitats such as stagnant ponds and deep underground have no oxygen.

• Organisms living there have can survive without oxygen; they must respire anaerobically all the time. These organisms include sonic worms, some bacteria and some fungi.

• Parasites that live inside other organisms, such as the gut parasite tapeworm and bacteria, also live in conditions that lack oxygen. They must also respire anaerobically.

• Living cells that normally respire aerobically can also respire anaerobically if oxygen is lacking. Animal and plant cells do this in different ways